Search

Photoconversion of CO 2 into value-added fuels has aroused widespread interest; however, this process is significantly limited by the inefficient thermodynamics and sluggish reaction dynamics in the diluted CO 2. To circumvent these obstacles, we design a bipyridine-based polyimide polymer for anchoring single Ni site for diluted CO 2 photoreduction. The desired Ni single atomic catalysts achieve high generation activity of ∼ 2262 μmol/h with apparent quantum efficiency (A.Q.E.) of 0.20% for CO 2 -to-CO in 0.1 atm CO 2 pressure. No measurable H 2 is produced in the catalytic process, affording nearly 100% CO selectivity over water splitting. This superior activity and selectivity outperform most previous atomical catalysts. Mechanistic analyses elucidate that the highly dispersed Ni atoms act as active sites for effective CO 2 binding and activation, and stabilize the rate-determining step of intermediates for CO generation. This work discloses the relationship between catalytic properties and single atoms for efficient solar-driven diluted CO 2 reduction. [Display omitted] • A novel Bpy-based polyimide polymer was fabricated for anchoring single Ni site. • Single-atom strategy leads to simultaneous increase of activity and selectivity. • Optimized Ni SACs for diluted CO 2 photoreduction to CO with nearly 100% selectivity. • CO 2 binding and activation with regulated intermediate are key for CO 2 reduction. [ABSTRACT FROM AUTHOR]

Photoreduction of diluted CO 2 is an effective strategy for the sustainable and environmentally friendly development of energy. In this study, lattice strain in NiSe is modulated through the control of the Ni concentration for the photoreduction of diluted CO 2. Refined XRD data and the results of the Williamson–Hall analysis indicate that the lattice strain is induced by lattice distortion caused by an absence of Ni atoms in the crystal lattice. In pure CO 2 , the cumulative CO yield and selectivity of Ni 1−x Se nanoflowers reached approximately 19.39 µmol and 90.7 % in 3 h, respectively. For lower CO 2 concentrations of 0.1 and 0.05 atm, the CO selectivity of Ni 1−x Se was approximately 72.7 % and 61.7 %, respectively. On characterization of the synthesized nanoflowers, we deduced that the lattice-strained Ni 1−x Se exhibited a favorable electronic band structure that improved the separation efficiency of the photogenerated carriers. DFT calculations results revealed that the lattice strain significantly facilitated the adsorption and activation of CO 2 , which resulted in highly efficient CO 2 photoreduction. This study provides an effective strategy for the design and synthesis of high-performance catalysts based on the modification of their crystal structures. [Display omitted] • Lattice-strained Ni 1−x Se nanoflowers were synthesized using the solvothermal method. • Lattice strain could be adjusted by modulating the Ni concentration. • Lattice-strained catalysts were utilized for the photoreduction of diluted CO 2. • Ni 1−x Se exhibited effective photocatalytic conversion of diluted CO 2 to CO. [ABSTRACT FROM AUTHOR]

• Novel frameworks with metalloporphyrin (ZFs-TCPP-Ni) have been constructed. • ZFs-TCPP-Ni framework serves as biomimetic photocatalyst to CO 2 photoreduction. • The biomimetic system exhibits a remarkable photocatalytic CO 2 -to-CO conversion. The development of biomimetic catalysis for efficient photoreduction of CO 2 is an effective alternative to address energy problems. However, amelioration on the construction of biomimetic catalysts for elevated photocatalytic performance is still challenging and demanded. Herein, a bioinspired artificial photosynthesis system is constructed based on ZrO 2 nanoframes (ZFs) and metalloporphyrin to mimic the morphology of trees. The robust backbone of the framework and the bio-inspiring porphyrins anchored on the surface of ZFs function as the strong trunk and well-ordered leaves of a tree, respectively. The biomimetic system achieves an evolution yield of 35.3 μmol during 3 h reaction with 93.1% CO selectivity and 1.84% CO apparent quantum efficiency (A.Q.E.), which is about 60.8 times larger than that of pure porphyrin (Ni) (0.58 μmol). Detailed analysis reveals that the catalytic system could not only achieve fast separation of the photogenerated carriers and effective CO 2 activation but also possess suitable energy levels, which could efficiently transfer electrons to the Ni catalytic sites to improve the photocatalytic activity. Furthermore, the good recycling tests could be explained by the robust supporting of frameworks as well as the strong binding of the Zr atoms and carboxyl groups of porphyrins. This work presents a simple model of biomimetic catalysts and outlines possible strategies for other biomimetic manufactures. [ABSTRACT FROM AUTHOR]

While semiconductor nanocrystals with different crystal forms typically show different catalytic performances, such behavior has been scarcely documented for metal-organic frameworks (MOFs). Herein, two Ni-MOF catalysts with different crystal forms have been successfully prepared and used in photo-reduction of CO 2. With a prolonged lifetime (5 h vs 2 h) and higher yield of the product CO (34 μmol vs 18 μmol), Ni-MOF(H 2 O) demonstrates a much better performance than Ni-MOF. Theoretical studies reveal that the adsorption energy of a CO 2 molecule is more negative on Ni-MOF(H 2 O) than on Ni-MOF (−0.85 eV vs −0.62 eV). Furthermore, the transfer and separation of the photo-generated charge carriers are also more efficient in the Ni-MOF(H 2 O) system. This study not only presents a superior Ni-MOF catalyst but also promotes the fabrication of highly active catalysts for the photo-reduction of CO 2. [Display omitted] • Ni-MOF catalysts with different crystal forms have been fabricated via a facile process for the first time. • Ni-MOF(H 2 O) exhibits a much better performance than the Ni-MOF in photo-reduction of CO 2. • Ni-MOF(H 2 O) system exhibits stronger adsorption ability for CO2 molecules and lower charge transfer resistance. • Ni-MOF(H 2 O) system also exhibits lower recombination rate of photo-generated charge carriers. [ABSTRACT FROM AUTHOR]

Photochemical CO 2 reduction to CO, acting as a mild and feasible method, holds huge prospects for atmospheric CO 2 level diminution. Non-noble metal aerogel has been supposed to be an appealing material in the field of catalysis, yet suffering from low conductivity and poor activity. From the perspective of electronic structure modification, oxygen-incorporated Ni aerogel is prepared by a facile reduction-oxidation method. With the optimized electronic structure in Ni@NiO-2 aerogel by oxygen incorporation, brilliant photocatalytic activity with CO yield of 39.30 μmol/mg and CO selectivity of 94.4 % could be achieved, taking advantage of the electron-rich Ni and greatly increased conductivity as well as sufficient active sites exposure. This work sheds light on the design and development of high-performance non-noble metal-based systems for catalytic CO 2 utilization. [Display omitted] • Nickel metal aerogel with porous network morphology exhibited outstanding activity. • Oxygen incorporation tuning leads to the electronic structure modification of Ni. • Optimized Ni with high conductivity promotes charge separation and CO 2 adsorption. • In situ FTIR and Mott-Schotty analysis imply the CO 2 -CO photoconversion mechanism. [ABSTRACT FROM AUTHOR]

Recently, energy storage system (ESS) with carbon dioxide (CO 2 ) as working fluid has been proposed as a new method to deal with the application restrictions of Compressed Air Energy Storage (CAES) technology, such as dependence on geological formations and low energy storage density. A novel ESS named as Compressed CO 2 Energy Storage (CCES) based on transcritical CO 2 Brayton cycle is presented in this paper. The working principle of CCES system is introduced and thermodynamic model is established to assess the system performance. Parametric analysis is carried out to study the effect of some key parameters on system performance. Results show that the increase of turbine efficiency is more favorable for system optimization and the effect of minimum pressures on system performance is more significant compared with maximum pressures. A simple comparison of CCES system, liquid CO 2 system and Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) system is conducted. It is shown that the system efficiency of CCES is lower than that of AA-CAES system but 4.05% higher than that of liquid CO 2 system, while the energy density of CCES system is 2.8 times the value of AA-CAES system, which makes CCES a novel ESS with potential application. [ABSTRACT FROM AUTHOR]